1. Technical Field
The present invention relates in general to the field of data processing systems and in particular to the field of data communication systems. Still more particularly, the present invention relates to a method and system for automatically determining a data communication device type and a transmission speed associated with the data communication device type.
2. Description of the Related Art
Electronic communication is increasingly common in the world today. For example, messages or documents may be transmitted between parties separated by great geographic distances utilizing modems, facsimile or voice communication systems.
Those skilled in the art will recognize that a modem is used to convert digital bit stream into analog signals that are sent over telephone or other transmission lines to a second modem. The second modem receives the analog signals and reconverts the analog signals back to a digital bit stream. The specific techniques used to encode the digital bit stream into analog signals are called modulation protocols. The various modulation protocols define the exact method of encoding and the data transmission speed.
Transmission speeds vary depending on which type of modem is used. For example, modems can transmit at 9600 bits per second (bps), 2400 bps, 1200 bps or 300 bps. The modulation protocol also identifies whether the modem utilizes frequency-shift keying (FSK) or phase-shift keying (PSK) to encode the data. As known in the art, under FSK the transmitted signal shifts back and forth between two frequencies: one representing a one and the other representing a zero. PSK utilizes shifts in phase to signal ones and zeros.
For modems to be able to transfer data, the modulation protocol of one modem must coincide with the modulation protocol of the second modem. Those skilled in the art will recognize that modems can negotiate certain features, such as error control, data compression, and transmission speed. One method used to negotiate these features is for a modem to first attempt to establish a connection at selected features, and if unsuccessful, to fall back to alternative features.
One feature that is also negotiable is FSK or PSK data encoding procedures. As known in the art, negotiation for data encoding can occur when a separate set of transmit and receive hardware for each supported modem type is provided. The negotiation process is accomplished by connecting each separate set of transmit and receive hardware to the transmission line. Once the negotiation process is successfully completed, only the transmit and receive hardware for the specified modem type remains coupled to the transmission line. All the other separate sets of transmit and receive hardware sits idle for the duration of the data communications. This can become costly in terms of hardware requirements, power requirements, and physical space requirements.
Therefore, it should be obvious that a need exists for a method and system for establishing data communications with modems which minimizes the need to duplicate communication hardware.